Lean Manufacturing Tools and Techniques

The article below outlines some of the key lean manufacturing tools and techniques.

Quality Function Deployment (QFD)

QFD is a helpful lean manufacturing tool for quality planning, which is also known as the "House of Quality". This is used in lean manufacturing environments to identify the outputs required by customers, and then trace these outputs to causal inputs which can be controlled by the organisation. This will typically include product design and manufacturing process characteristics. As such, QFD can be used to identify which manufacturing process characteristics are key drivers of product and service quality for the customer. The output of QFD Phase 1 is Design Requirements. This is the input into QFD Phase 2, whose output is Critical Part Characteristics, which is the input to QFD Phase 3 whose output is Key Process Parameters, which is the input to QFD Phase 4 whose output is Production Requirements.

Process Failure Modes and Effects Analysis (FMEA)

Closely related to the Design FMEA, is another lean manufacturing tool: Process FMEA studies can be used by a lean manufacturing consulant to size the relative risks of a range manufacturing quality failure modes. It is a formalized analytical technique which lists all potential sources of failure and then allocates a weighted points score according to the expected frequency, the likelihood of being able to detect the failure and the severity of the consequences. It is used to ensure that all manufacturing failure modes have been evaluated. This priorities design risks with a view to them being eliminated.

Poka Yoke or (Fool-Proofing)

Often an extremely cost-effective lean manufacturing tool, using very simple devices to prevent the production of defective products. There are typically three types: 1. Contact Type, 2. Constant Number Type, 3. Performance Sequence Type.

Statistical Process Control (SPC)

In lean manufacturing environments this is considered to be an extremely effective quality tool, requiring only periodic measurement of system output variables, and thus low administrative costs, yet because it is preventive, also reduces process non-conformance dramatically. SPC is a core element within the six-sigma toolkit. It involves establishing the limits of statistical variability for a system output parameter in steady state conditions (see Machine Capability Studies). Limits for the variability of the process are calculated and control limits set, which mean that when not under steady state conditions and the output variable either falls below the lower control limit, or climbs above the upper control limit the process, the process can be halted and remedial action taken. If the system is "capable", then the upper and lower control limits will be within the tolerance required of the system and the remedial action can be taken before the output variable is out of tolerance.

Machine Capability Studies

Another extremely important preventive quality approach in the lean manufacturing toolkit. SPC techniques are used establish the statistical variability of an output parameter from a machine in steady state conditions. If the engineering tolerances required by products produced by the machine are within its steady state limits of variability, the machine is said to be "capable" of the tolerances. Process capability studies are broader than machine capability studies, in that they typically also take account of the intervention of other actors (e.g. a human operator) in addition to the capability of a machine.

Six Sigma

Six Sigma has grown to become an entire range of quality tools and techniques in its own right. In environments like GE, the six sigma approach has broadened to include such things as programme and project management tools and rules all of which are complementary to lean manufacturing. The original concept however is that embodied by SPC and Capability Studies - that is; the need for ever tighter consistency of process variables.

Taguchi

When the interactions between a large number of input parameters are complex, yet their combined effect causes a range of outcomes for output parameters, normally the only way to understand the combined effect of differing input parameter values would be to conduct an experiment for every possible combination (full factorial) of input parameter values. By contrast the Taguchi (design of experiments) methodology enables a much smaller number of experiments on the input variables to be conducted, which nevertheless provide an equivalent understanding as if the full factorial range of experiments had been conducted. Its statistical validity has been questioned by some, but exponents of the approach cite its noticeable successes in enabling complex quality problems to be solved. This is a very valuable lean manufacturing tool.

Shainin

In some ways like Taguchi, but a range of statistical tools and techniques for developing an understanding regarding the complex interactions between a significant number of input variables and output variables. Again a powerful means of eliminating waste - a fundamental principle of lean manufacturing. Examples of techniques include "Multi-vari Charts".

Reducing Cycle Times/Reducing Lead Times - Cellular Manufacturing Architecture

Since in many organisations, the sum of machine cycle times is typically only 5% of the entire lead time for the manufacturing of that product, (best practice is 50%) the driver of product lead times is not the speed at which machines process components. Often the most significant driver of lead times (and therefore work in progress & cash) is the number of changes in ownership during a component's manufacturing route. This is often the case in "process" or "functional" manufacturing architectures, where similar processes are grouped together and components travel many times between groups of processes, changing ownership throughout. On the other hand, a "Cellular" manufacturing architecture, can be introduced to minimize changes of ownership; grouping disparate processes together for components with similar characteristics. Moving from a "functional" to a "cellular" manufacturing architecture can reduce WIP and lead times by at least 50%, and can also reduce the need for substantial indirect labour (e.g. expediters, material handlers, supervisory staff etc). Typically headcount reductions of between 20-30% are reliable.

Kanban

Kanban means "sign" in Japanese, and is a visual reactive re-order point control system. Reactive in the sense that without intervention it cannot anticipate peaks or troughs in demand and adjust accordingly, and a re-order point system because when a minimum inventory level is reached, a reorder Kanban is launched. A lean manufacturing consultant can select an optimum design from a number of variations on the theme; single card Kanbans (move and make card), dual card Kanbans (move card and make card). True Kanban however, can be applied to components of any value, but is most reliable when demand is predictable and flat. As with any reactive reorder point system Kanban can be caught out by peaks in demand, and can hold unnecessary costly work-in-progress if demand drops. As such, it works best in an environment which is subject to Level Scheduling. A two-bin system is a variation on the Kanban theme, used for low value components, where inventory value is negligible and level scheduling isn't necessary.

Level Scheduling

Ask any lean manufacturing consultant and they'll tell you that Level Scheduling is a very under-rated technique, because it is often a major cost driver and is a key pre-requisite for robust and low WIP Kanban implementations. It relies heavily upon quick changeovers (SMED) to ensure that manufacturing processes can make say components A, B & C in smaller quantities every day of the week, rather than A for 3 days, then B for 2 days and then C for 2 days. This ensures that demand throughout the manufacturing system for upstream specialist resources (e.g. a special process for component B) doesn't come in peaks, but is spread evenly. This enables the number of scarce specialist resources in a lean manufacturing system to be minimized (e.g. reduced labour, machines etc), and Kanbans to recirculate more frequently and for their re-order point levels to be dropped (reducing WIP). It is a key means of driving out variability in a lean manufacturing environment.

Quick Changeovers or Single Minute Exchange of Die (SMED)

A core tool for a lean manufacturing consultant, SMED is often used by because of its multi-faceted impact. Primarily it enables a manufacturing organisation to move from a "minimum batch quantity" approach to a "batch of one" approach, but this also facilitates Level Scheduling, which in turn facilitates robust and low WIP Kanban implementations. Changeovers are analysed into "external" elements, those which can be performed off-line whilst the machine is running and "internal" elements which have to be performed when the machine is stopped. As many internal elements are converted to external elements as possible and then both internal and external elements are streamlined as far as possible.

Mixed Mode Manufacture

Involves the development of tooling which rather than performing an operation on multiples of one type of component (e.g. an eight cavity plastic injection moulding tool for salt shaker lids and another for pepper shaker lids) can be replaced by an eight cavity tool split into four cavities for salt shakers and four cavities for pepper shakers. This eliminates changeovers and ensures that production schedules can be "levelled".

Bottleneck Process Management

Unfortunately bottlenecks move depending upon mix, but because they govern the output from the entire system, if capacity is stretched multi-shift them, work them through breaks, minimize changeover times and minimize downtime using Total Productive Maintenance techniques etc.

Total Productive Maintenance (TPM)

Another lean manufacturing tool, which is focused on the objective of zero breakdowns. Significant emphasis is on first line preventive maintenance by operators, which is then supported by a regime of preventive maintenance provided by specialists. In order to make planned or preventive maintenance work successfully, it is often necessary to separate it organizationally from breakdown maintenance.

Nagare

Operators "walk" products around a "U-shaped" cell of simple machines manually loading products from previous processes into the next. Each machine once loaded operates automatically. Cell capacity can be increased by adding more workers into the cell. Benefits include: improved labour productivity, lower capital expenditure, flexibility, lower level skill requirements. A technique still not seen so often in UK manufacturing facilities.

Simulation

There are two types of manufacturing system simulation: computer and manual. Whilst real-time computer graphics are great fun to watch, but lean manufacturing specialists find the greatest value is achieved when manual simulations are played by operators (like a board game) to test the robustness of a manufacturing system design and in particular to design Kanban systems. This approach enables operators to "buy-in" to the design of the manufacturing system.

5S

5S is a series of five simple lean manufacturing tools to improve the workshop environment. Whilst the benefits that 5S can bring are not "step change" in nature, the approaches can significantly reduce losses in productive time for example by ensuring that tools are not mislaid, but are readily to hand on say shadow boards. The approaches can also be helpful in lean manufacturing environments in establishing cleanliness and tidiness norms for an organisation and therefore making a contribution towards limited cultural change.